Soil additives immobilising heavy metals in contaminated soils

Addition of iron oxides, lime, clay minerals and other substances can be used to decrease the plant availability of toxic heavy metals such as Pb, Zn, and Cd. Extractability and consequently plant concentrations may be reduced in some cases by more than 50%. The assessment of remediation processes is supported by biomonitoring methods in the field with Plantago lanceolata and in the greenhouse by barley test experiments, in combination with extraction by ammonium nitrate.

A Novel Clean Biopolymer-Based Additive To Improve Mechanical And Microstructural Properties of Clayey Soil

Conventional soil additives, as a sector of construction materials, can cause serious environmental problems due to their cement-dependent nature. To eliminate destroying effects of these kinds of additives, environmentally friendly ones have gained great consideration. Although polysaccharides are considered as powerful biocompatible soil additives in recent studies, the effect of their crosslinked hydrogel with elevated rheological and adhesive properties has been very rarely investigated in soil stabilization. In this paper, calcium chloride was used as ionic crosslinker to enhance recently proposed Persian gum biopolymer as a novel polysaccharide-based additive for clayey soil stabilization. A group of macro and micro scale tests including unconfined compressive strength (UCS), direct shear test (DS), freeze thaw durability, scanning electron microscopy (SEM), stereo zoom microscopy (SZM), Brunauer, Emmett and Teller (N2-BET) and X-ray diffraction (XRD) were conducted. The tests were also performed on soil treated with xanthan gum as a common hydrocolloid of soil stabilization. As the results show, the introduced ionic crosslinked hydrogel at its optimum content has superior performance than well-known xanthan gum in terms of soil strength and ductility. Crosslinking has also positive effects on durability results of pure Persian gum to make it comparable to xanthan gum. Consumption of lower amounts of Persian gum at presence of ionic crosslinker can make stabilization projects more economical efficient. Microscale tests also confirmed the powerful impact of optimum modified hydrogel on soil interstructure by filling the pores, agglomeration of soil particles and formation of new cementitious compounds in the mineralogical structure of the soil.

Cultivation of industrial hemp using solid and liquid residues from municipal composting

<p>Industrial hemp as a renewable raw material for fiber extraction like for construction material or as biomass for energy generation is a potential agricultural product for low productive soils in temperate climates. Soil and climate conditions in Lower Lusatia, South Brandenburg, generally qualify this region suitable for growing industrial hemp. But due to the nutrient requirements of the plants, fertilization is necessary for optimal growth. Fertilization on sandy soils is, however, often problematic, since the groundwater risk is increased by the entry of nitrogen and phosphorus from the fertilizer supply. In addition, the costs of fertilizers make resource-efficient and sustainable use of the locations problematic. The liquid phase obtained in the course of municipal composting would be a suitable fertilizer in terms of nutrient concentrations, but due to the potential risk to groundwater, the use of the liquid phase from composting is currently not feasible. The aim of the project is the development of a closed cultivation system for industrial hemp using hydroponics, whereby sand and pelleted soil additives from composting are used as a supporting substrate. Nutrients from the liquid phase from the municipal composting will be used as fertilizer. The cultivation will take place under controlled conditions (light, temperature, watering water and leachate) in a glasshouse experiment. A mixture of sand and pelletized soil additives is to be tested as a plant substrate in various additional amounts. The sandy substrate is representative for the soils in Lower Lusatia. The use of pelletized soil additives in combination with the liquid phase from municipal composting is an innovative process and on the one hand contributes to the development of a new sales market and on the other hand promotes the local and resource-saving use of recyclables in the sense of the circular economy. The use of hydroponics is a promising process that can be used regardless of the climate and without endangering soil and groundwater.</p>